High pressure water tube steam generator



Dec' 3 1935- H. c. EGLOFF HIGH PRESSURE WATER TUBE STEAM vGENERTR Filed Aug. 9, 1953 o o l ooooooooooo wowowomow n oooooooo QM. NN m Inn/ENTER M/ M /J B/ W mi #M Pited Dec. 3, 1935 HIGH PRESSURE WATER TUBE STEAM GENERATOR Hans Conrad Egloff, Winterthur, Switzerland, as-

signor to lirm Sulzer Frres Socit Anonyme, Winterthur, Switzerland Application August 9, 1933, Serial No. 684,331 In Switzerland October 10, 1932 1 Claim.

This invention relates to high pressure water tube steam generators oi the once through type, that is to say in which the working medium is fed to one end of a continuous tube and is discharged from the other end as steam or vapour.

With a View to preventing water particles from being carried along with the steam to the points of consumption it has been proposed to make the length of the tube at least ten thousand times the internal diameter of the tube and to provide, between the generator and the point of consumption, a throttling device, the ei'iective crosssectional area of winch is automatically regulated in accordance with the steam pressure within the tube. If however not only the tendency for wet steam or particles of water to be delivered from the outlet end of the generator but in addition the danger oi overheating the tube walls is to be overcome, it is also necessary to make the length of the path traversed by the medium through the generator such that it exceeds a denite minimum value, and to cause the pressure ci the working medium to iall gradually from the inlet to the outlet of the tube by a predetermined value. The present invention has for its object to provide an improved generator which, whilst capable of producing at least three tons of steam per hour, will overcome the above diiiiculty.

To this end a steam generator according to the invention and capable of producing at least three tons of steam per hour comprises at least one continuous tube arranged partly in the combustion chamber and partly in the ilues with a length not less than three hundred metres and at least ten thousand times the mean internal diameter of the tube, the pressure at the inlet end of the generator exceeding that at the outlet end by at least twenty atmospheres without any sudden pressure drops taking place within the tube, and a flow vibration damper arranged between the point of delivery from the tube and the point of steam consumption whereby the cross-sectional area available for the ow of steam from the generator is increased or decreased respectively in accordance with increase or decrease of the pressure within the tube on the inlet side of the damper.

In this way not only is the velocity of flow within the generator such that a iine froth-like mixture of the water and steam is formed but, in addition, the flow vibration damper tends to damp out oscillations in the iiow of the working medium due, for example, tovariations in the quantity of steam drawn from the generator.

The How vibration damper is not in the nature oi a safety valve or a steam reducing Valve as hitherto employed in steam pipe lines, but operates to damp out oscillations of flow which, if unchecked, are liable to reach dangerous dimen- 5 sions du'e to the great length and therefore total elasticity of the generator tube. Furthermore such oscillations are liable to result in such rapid acceleration of flow of the medium that wet steam or particles of water tend to be carried from that 1()v part of the generator containing wet steam to the apparatus supplied with steam from the generator, which apparatus is liable to be thereby damaged. In this respect it will be understood that the flow of wet steam through the generator l5 to the outlet end is liable to damage apparatus to which the steam is supplied rather than to damage the generator itself.

The above-mentioned minimum output of the generator, the quantity of working medium, the 20 minimum ratio between tube length and tube diameter, the minimum length of the tube, and the gradual pressure drop within the tube being at least 2O atm., are mentioned in order to illustrate the invention and not in order to limit the 25 scope of the invention. The given gures, however, contribute to determine the invention, insofar that by means of them, as has been determined by tests, the processes within the tube take place in such a way that the working medium in 30 the tube, where consisting of water and steam, is converted into a ne froth-like mixture in consequence of the resulting velocity of flow.

One construction of steam generator according to the invention is illustrated somewhat dia- 35 grammatically and by way of example in the accompanying drawing.

In the construction illustrated working medium is fed by a feed pump l to the inlet end 2 of the generator which comprises a continuous tube 3a, 40 3b, 3c, 3d, 3e and 3f, the portion 3f, which is approximately SSO metres in length, being arranged so as to screen the walls of the combustion chamber whilst the remaining portions of the continuous tube have a total length of approxi- 45 mately eight hundred metres and are disposed in the ues. The total length of the continuous tube is thus about one thousand three hundred metres. For the sake of clearness the separate portions 3a, 3b, 3c, 3d, 3e and 3f are shown in the 50 drawing as communicating through pipes which pass outside the brick work of the generator. The steam generated is delivered from the outlet end 4 of the generator to a delivery pipe 5, the necessary heat being supplied by fuel burnt on a 55 within a chamber grate 6 the hot gases passing through the flues to an outlet flue 'i after which the residual heat in the gases may be utilized.

The generator illustrated is intended Vfor a normal output of eighteen tons of steam per hour Vat a pressure of one hundred atmospheres and a temperature of 450 C. The working medium enters the tube at the inlet end 2 at a pressure of approximately one hundred and fty atmospheres and a temperature of approximately 100? C. The internal diameter oi the tube is about thirty-six millimetres over a length of approximately nine hundred metres from the inlet end whilst the remaining four hundred metres has an internal diameter of about forty-eight millimetres so that the mean internal diameter ofthe tube as a whole is approximately forty-one millimetres. The working medium is raised to evaporation ternperature in the rst seven hundred metres approximately, evaporation taking place in the succeeding three hundred metres and superheating in the remaining three hundred metres.

Y Since the steam is generated at approximately a hundred atmospheres and the pump supplies medium at approximately a hundred and'ftyV atmospheres, an excess pressure of iifty atmospheres exists at the inlet end of the generator. This excess pressure causes turbulence in the medium as this flows through the tube and in addition results in the velocity of ow in the first part of the tube being in the nature of two metres per second, this velocity increasing still further in the evaporating Zone and reaching a value as high as ten metres per second when the medium reaches the end oi the portion 3e. The water iiowing through the tube thus tends to mix with the steam as soon as this is generated, thereby forming a fine froth-like mixture of water and steam.

A flow vibration damper, generally indicated at 3, is provided between the delivery pipe 5 and the point or points of consumption (not shown), the object of the flow vibration damper being to maintain the ilow oil working medium substantially uniform and/or to damp oscillations in the flow of the working medium within the generator. In the construction illustrated the delivery pipe 5 communicates, at a point l5 in its length, through a pipe |55 with a device to which pressure medium is supplied through a port I8, a port |9 being provided through which this medium can be released from the device |'V|. Arranged within the device is a piston comprising a lower portion 2@ and an upper portion 2| having lateral ports as shown. The piston 2| can reciprocate 22- which communicates through a pipe 23 with two cylinders 24 in a control device 25.

Pressure medium is supplied to each of the cylinders 24 through an inlet port 26, and can be discharged from the cylinder through an outlet port 2. Each cylinder of the control device 25 communicates through a pipe 28 with a pressure chamber 29 or a servomotor forming part of the flow vibration damper B. Arranged to reciprocate within each cylinder 24 is a piston valve 33, one of these piston valves being loaded by a spring 3|a whilst the other is loaded by a spring Sib, the tension of the spring 3 la being less than that of the spring 3|b. Each of the pressure chambers 2Q contains a piston 32, one of which, i. e. that associated with the piston valve loaded by the'spring 3M, is rigidly connected to a valve 33 whilst the other piston 32 which is associated with the piston valve loaded by the spring 3|b is rigidly connected to a valve 34. The valves 33 and 34 are arranged in a casing 35 having outlets 5a and 33 on the underside of the valves 33 andl 34 respectively.

The operation of the flow vibration damper 5 is then as follows:-' Y

If the steampressure within the delivery pipe 5 increases the piston 20, 2| will be raised until the ports in the piston 2| communicate with the inlet port i8. Thus pressure medium enters through the inlet port |8 and thereby tends to equalize the pressure on the two ends of the piston 26, 2|, and since, if the pressure within the cylinder 22 is sufficient to move the piston 20, 2| Y downwards against the pressure of the steam until the port in the piston 2| communicates with the outlet I9, the pressure within the cylinder 22 will be again reduced to a value corresponding to the steam pressure in the delivery pipe 5. Thus the pressure within the cylinder 22 will be maintained 20 substantially equal to that in the delivery pipe 5.

When therefore the pressure at the point |5 in the delivery pipe 5 increases the pressure in the cylinder 22 will increase accordingly, Whereby the piston valve 33 loaded by thespring 3|a 25 will rst be raised so that pressure medium delivered through the port 26 will pass through the pipe 23 associated with the piston 32 connected to the valve 33 so that this valve is opened. The effective cross-sectional area available for flow of steam from the delivery pipe 5 to the point of consumption is thus increased thereby reducing the pressure at the point I5 in the delivery pipe 5. If the pressure in the delivery pipe 5 increases to such a value that even when the valve 35 33 is fully open the increase of steam pressure continues, the piston valve 3i! will be raised against the control spring 3|h` so that pressure medium delivered through the port 26 will pass through the pipe 28 and act on the piston 32 40 associated with the second valve 34. In this way the crosssectional area available for the flow of steam from the delivery pipe 5 will be still further increased thereby reducing the pressure within the delivery pipe and thus Counteracting the tendency for the pressure within the generator to increase. The steam which iiows through the valve 34 preferably passes through a pipe 36 which leads to a point of consumption at a lower pressure or to a steam accumulator, not shown.

It will Vbe understood that the difference between the tension of the spring 3|a and that of the spring 3|b is such that the valve 34 in the casing 35 only begins to'open after the valve 33 55 of the casing 35 has been fully opened.

Thus the valve 34 will be opened when the steam pressure is excessive and the point or points of consumption supplied with steam through the valve 33 require less steam than the generator 60 is producing.

When the steam pressure within the delivery pipe 5 decreases the pressure Within the'cylinder 22 falls accordingly. If both the valves 33,

V34 are then open the piston valve 30 associated 55 with the valve 34 will first move downwards so that pressure medium is released through the outlet port 21 whereby the effective Ycross-section through the valve 34 will be reduced. After the valve 34 is closed and assuming that the fall of 70 pressure within the generator continues the piston valve 30 associated with the valve 33, will move downwards to reduce the effective cross- Vsection availablethrough this valve. The crossse'ctional area available for the flow of steam from 75 the delivery pipe 5 to the point of consumption is thus decreased so that the steam pressure in the delivery pipe 5 will again tend to rise Whereby the tendency for a rapid drop in the pressure within the generator will be overcome.

It will thus be seen that by means of the iioW vibration damper 8, when the pressure in the delivery pipe on that side oi the damping device adjacent to the generator, i. e. at the point I5, tends to rise the cross-sectional area available for the ow of steam is increased so as to counteract this rise of pressure. Similarly when the steam pressure tends to fall the cross-sectional area available for the flow of steam from the delivery pipe 5 will be reduced so as to counteract such fall in pressure. In this way oscillations of flow of the working medium, which oscillations are liable to be intensied due to the great length of the tube, are damped so that rapid accelerations of iiow of the medium which would tend to cause water particles to be delivered with the steam are prevented.

It will be understood that the construction above described is given by way of example only and that details may be modiiied Thus, for eX- ample, in the case of large generators the medium may pass through two or more tubes connected in parallel. If this is done however the length of each tube shall be not less than ten thousand times its internal diameter and the total length of each tube will, in accordance with the invention, be not less than three hundred metres. When using several tubes connected in parallel, working medium may be supplied to each tube by a separate feed pump, but if desired a single feed pump may supply working medium to several of the tubes and means may be provided whereby two or more tubes connected in parallel may be temporarily connected in series. Further, if several tubes connected in parallel are employedA same throughout the length of each tube or if desired the diameter of each tube may be increased gradually or step by step in the direction of flow of the medium provided that interruptions in the continuity of the tube, as by the inter- 5 position of drums, steam separators or throttling points, are avoided and sudden pressure drops within the tube thus prevented. The speed of flow of the Working medium at the outlet end of the generator must not exceed seventy to eighty metres per second and the temperature of the medium fed to the generator may if desired be more or less than 100 C.

I claim:

In a steam generator capable of producing super-heated gases in an amount of not less than three tons per hour which comprises a continuous tube having a length of not less than 300 meters and being at least 10,000 times the mean diameter of said tube, means for supplying working medium to one end of said path at a high pressure but below the critical pressure, whereby said pressure forces said medium through said tube, means for gradually lowering the pressure of said working medium at a substantially uniform rate from the beginning of the continuous tube to the desired pressure at the end of said tube, means for producing combustion of fuel and damping means for diminishing the fluctuations of flow within said tube, said damping means being located between the ends of said tube and the point of consumption of said gases, said damping means comprising an outlet conduit, a steam pressure responsive device therein and having pressure-responsive actuating means, a double cylinder control device having one end of the cylinders connected to said means and spring controlled piston valves in said cylinders, one of the springs being weaker than the other to cause one of said valves to open at lower pres- (0 sure than the other, means operable by said valves for increasing at higher pressures and decreasing at lower pressures the effective crosssection of said outlet conduit, whereby the pressure at the outlet end of said continuous tube can be maintained substantially constant.

HANS CONRAD EGLOFF. 

